Genome of a novel circovirus of starlings, amplified by multiply primed rolling-circle amplification.

The genus Circovirus comprises small non-enveloped viruses with a circular single-stranded DNA genome. By using PCR with degenerate primers, a novel circovirus (starling circovirus, StCV) was detected in spleen samples of wild starlings (Sturnus vulgaris and Sturnus unicolor) found dead during an epidemic outbreak of septicaemic salmonellosis in northeastern Spain. Using a specific PCR, StCV was also detected in apparently healthy birds from the same population. The genome was amplified using multiply primed rolling-circle amplification and cloned. Open reading frames (ORFs) with similarities to the replication-associated protein and the capsid protein of circoviruses as well as an additional ORF encoding a protein of 106 aa were evident from the sequence. Phylogenetic analysis of circovirus genomes revealed the highest degree of similarity (67.1 %) between StCV and canary circovirus. A similar analysis of the evolutionarily conserved cytochrome b gene of the circovirus host species revealed a strict co-evolution of circoviruses with their hosts; however, the circoviruses showed about a threefold higher genetic divergence than their hosts.